X100管线钢激光焊接接头显微组织及耐腐蚀性能研究

Research on Microstructure and Corrosion Resistance of X100 Pipeline Steel Laser Weld Joints

利用IPG公司YLS-6000型光纤激光器对X100管线钢进行了激光拼焊,研究了热输入对焊接接头的宏观形貌、显微组织、力学性能及耐腐蚀性能的影响规律。研究结果表明,随着热输入的减小(150→129→113J/mm),焊接接头宽度及焊缝的凹陷量均逐渐减小,相对比而言热输入为113J/mm时获得的焊接接头宏观形貌最佳。三种热输入条件下焊接接头各微区的显微组织类型未发生明显变化,焊缝区和粗晶区组织均为板条马氏体,细晶区组织以马氏体为主但存在少量的贝氏体,混晶区组织则为贝氏体和铁素体的混合组织。热输入对焊接接头各微区硬度值的影响不明显,焊接接头峰值硬度均位于焊缝和粗晶区附近,为346HV左右;细晶区随着远离焊缝中心硬度逐渐下降,混晶区硬度达到最低值,为283 HV左右。三种热输入条件下混晶区内均出现软化区,软化区宽度、硬度降幅均随着热输入的减小而减小。焊接接头的耐腐蚀性规律为:焊缝最差,热影响区次之,母材最佳,其主要原因在于焊缝区和热影响区组织内部均包含高位错密度的马氏体,导致其耐腐蚀性恶化。

The laser welding of X100 pipeline steel was carried out by using IPG YLS-6000 type fiber laser,and the influence of heat input on the macro morphology,microstructure,mechanical properties and corrosion resistance of the welded joint was investigated.The results show that with the decrease of heat input（150→129→113 J/mm）,the width of weld joint and the dent amount of welding seam decrease gradually.In contrast,the heat input is 113 J/mm the welding joint obtained the best macro morphology.Under the three heat input conditions,microstructure of the welded joints did not change significantly,the weld zone and the coarse grain zone are lath martensite,the fine grain zone is mainly martensite,but there are a few bainite,and the mixed grain region is a mixture of bainite and ferrite.The influence of heat input on the microhardness of the welded joints is not obvious,the peak hardness of welded joints is located near the weld and coarse grain region,which is about 346 HV,and the hardness of the fine grain region decreases gradually from the center of the weld center,and the hardness of the mixed grain region reaches the lowest,about 283 HV.Under the three heat input conditions,the softening zone appeared in the mixed grain region,and the softening zone width and hardness decrease with the decrease of heat input.The corrosion resistance of welded joints is as follows：the weld is the worst,the heat affected zone is second,and the base material is the best,the main reason is that the weld zone and the heat affected zone contain martensite with high dislocation density,which leads to the deterioration of corrosion resistance.